Clint Dempsey (New England Revolution to Fulham)

There were concerns when Clint Dempsey joined Fulham from the New England Revolution in the 2007 January transfer window for £2 million.

While he was considered one of the best players in Major League Soccer, he had never won the MLS MVP or Golden Boot award, so would he be able to make the step up?

Then there were attitude issues: he had punched his then team-mate Joey Franchino and had served a suspension for violent conduct after elbowing Jimmy Conrad, who suffered a broken jaw.

Yet the upside Fulham saw in Dempsey came to fruition after hard work and dedication.

"Clint Dempsey always made the difference," then Fulham manager Martin Jol said last February, as per Matt McGeehan at The Independent. "I feel if Clint Dempsey hadn't been here over the last three or four years, we could've ended up with a real problem."

Now he has the chance to bail out Rene Meulensteen, Jol's successor, as Fulham fans hope Dempsey, on loan from the Seattle Sounders, can find his scoring touch again.

Sebastian Kehl (From Freiburg to Borussia Dortmund)

Before Mario Gotze, Robert Lewandowski and Torsten Frings, Freiburg's Sebastian Kehl was in the middle of a dispute between Borussia Dortmund and Bayern Munich.

When Bayern suggested transfer improprieties, Dortmund snapped back.

"We are not the ones who throw cheques at players who are contracted to other clubs," Dortmund sporting director Michael Zorc said, as per Frankfurter Allgemeine Zeitung (h/t Sky Sports). "Kehl has said to us quite clearly that he has not given Bayern an oral or written agreement."

At the time, Dortmund beat out Bayern in successive January transfer windows to a world-class prospect.

In 2001, it was Tomas Rosicky. The next year, it was Kehl, who has since played over 300 times for Dortmund.

Luis Suarez (From Ajax to Liverpool)

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When Luis Suarez signed from Ajax in the 2011 January transfer window for £22.8 million, Liverpool were receiving a diver, a biter, a troubled individual but the most outstanding Eredivisie talent since Ronaldo Luis, who was exceptional at PSV Eindhoven.

Suarez had scored 49 goals during the 2009-10 season for Ajax, so Liverpool were willing to accept his flaws as a human being.

It hasn't been easy for the Reds but their persistence and blind loyalty to Suarez is paying off.

With 20 goals in 15 Premier League games this season, Suarez won't factor in the 2013 FIFA Ballon d'Or but will be a contender for the 2014 Ballon d'Or.

Patrice Evra (From Monaco to Manchester United)

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How did Manchester United sign a left-back with world-class potential in Patrice Evra, who had competed in the 2004 UEFA Champions League final for Monaco, for just £5.5 million?

"We have been monitoring him [Evra] all season and it is fantastic he is joining us," then United manager Sir Alex Ferguson said, as per BBC Sport. "He is a good age and he is still developing as a player, which is always exciting."

This was January 2006 and eight years on, United have expended Evra's usability as a top-flight left-back.

In return, he has played a part in five Premier League winning seasons, lifted the Champions League trophy and appeared over 360 times for United.